Chinese spacecraft returns to Earth after mysterious 276-day mission.

An experimental Chinese spacecraft, whose details have not been disclosed, returned to Earth after 276 days in orbit, marking an "important" breakthrough in China's research into reusable spacecraft technology that will provide a more convenient and inexpensive way to mount future space missions. The spacecraft's technologies, altitude, and orbits have not been revealed, and no images of the craft have been released to the public. Chinese social media commentators have speculated that Beijing has been developing a spacecraft like the U.S. Air Force's X-37B, an autonomous spaceplane that can remain in orbit for years.